1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition. More specifically, it relates to a thermoplastic elastomer composition superior in processability and dynamic fatigue resistance even under a low temperature such as xe2x88x9220xc2x0 C. and also to a tire, particularly a tire suitable for use in a cold area, using the same as a tire member.
2. Description of the Related Art
To improve the dynamic fatigue resistance, while maintaining a balance between the flexibility and the gas permeation resistance, it is known from Japanese Unexamined Patent Publication (Kokai) No. 8-259741 that a nylon resin and a rubber component are formed into a thermoplastic elastomer composition by dynamic vulcanization, which is then used for an air permeation preventive layer (e.g., inner liner). However, there was the problem that the thermoplastic elastomer composition was not sufficient in dynamic fatigue resistance at a low temperature such as xe2x88x9220xc2x0 C. and, therefore, was not necessarily suitable for use, as a tire, in a cold area.
Accordingly, an object of the present invention is to provide a thermoplastic elastomer composition superior in dynamic fatigue resistance even under a low temperature such as xe2x88x9220xc2x0 C. and a cold region tire using this composition as a tire member.
Other objects and advantages of the present invention will be apparent from the following description.
In accordance with the present invention, there is provided a thermoplastic elastomer composition comprising a thermoplastic resin (A) and a rubber composition (B) dispersed in the thermoplastic resin (A), wherein a stress at the time of 2.5% elongation in a stress-strain curve of the thermoplastic elastomer composition is 0.1 to 50 MPa and a ratio of the stress (M200) at xe2x88x9220xc2x0 C. and 200% elongation and the stress (M100) at xe2x88x9220xc2x0 C. and 100% elongation is 1.0 less than M200/M100 less than 2.0.
In accordance with the present invention, there is also provided the above thermoplastic elastomer composition, wherein the value of the first order differential of the stress-strain curve of the thermoplastic elastomer composition monotonously decreases in a 2 to 20% strain region.
In accordance with the present invention, there is further provided the above thermoplastic elastomer composition, wherein an air permeation coefficient at 30xc2x0 C. of the thermoplastic elastomer composition is more than 25xc3x9710xe2x88x9212 cc cm/cm2xc2x7secxc2x7cmHg and not more than 100xc3x9710xe2x88x9212 ccxc2x7cm/cm2xc2x7secxc2x7cmHg and a Young""s modulus at xe2x88x9220xc2x0 C. is not more than 250 MPa.
In accordance with the present invention, there is still further provided the above thermoplastic elastomer composition, wherein the thermoplastic resin (A) is a polyamide resin having the rubber component (B) dispersed therein, at least one member selected from the group consisting of polyamide plasticizer (C1) and thermoplastic elastomers (C2) is contained in the composition and a ratio of the components, where the total is made 100% by weight, is as follows:
(A) polyamide resin: 15 to 59% by weight,
(B) rubber composition: 40 to 70% by weight, and
(C) polyamide thermoplastizer+thermoplastic elastomer (C1+C2): 1 to 30% by weight.
In accordance with the present invention, there is still further provided the above thermoplastic elastomer composition, wherein the elongation at break at xe2x88x9220xc2x0 C. is not less than 300%, the Young""s modulus at xe2x88x9220xc2x0 C. is in a range not more than 250 MPa, and the product of the elongation at break and the Young""s modulus is 10,000 to 100,000 (%xc2x7MPa).
In accordance with the present invention, there is still further provided the above thermoplastic elastomer composition, wherein the ratio, by weight, of composition of the components satisfies the following relation:
1.0xe2x89xa6(B+C2)/(A+C1)xe2x89xa62.5 
In accordance with the present invention, there is still further provided a tire using the thermoplastic elastomer composition.